No age given for either Cath Looney burial (very few ages were recorded at that time in Maughold).

Yes, the child was often known by the father's surname even when the mother married someone else, or didn't marry.

You can see this with illegitimate children born in the 1800s, and their census entries. Sometimes they reverted to the mother's name for one or two censuses, and were under the father's surname for the others, and when they married. Or would have their father's surname in all records.

Your guess is as good as mine with which wills to look at - sorry. I found most ones by accident when looking through all wills for a parish on a film I had ordered. It was often a grandparent's will naming their son or daughter's illegitimate child, or the father leaving something for his illegitimate child's education or apprenticeship.

This is an example:
http://www3.telus.net/lawson/twill/1788_019.html

Before seeing this will I had only the baptism which read "Charles illegitimate son of Chas Joughin & Margt Christian baptized 4th October 1778" [Andreas par reg.], and had no idea which of the many Margaret Christians the mother was. The son was always known as Joughin, and it turned out that his mother had died soon after his birth.

Sue